It has been my experience, with 40 years as a wedding photographer, that most forgotten people when it comes to photos at a wedding are often individual parents of bride and/or groom.
Most photographers will be sure to include parents in photos with bride and groom, but most will never think to inquire about doing groups of individual dads of bride or groom with all his brothers and sisters who are present at wedding. And of course, same is true with individual moms of bridal couple, too.
While you're getting these photos taken, be sure to include any parents and grand-parents of those brothers and sisters that are there, too, to capture their entire core family group in photos.
A wedding is almost perfect place to take these kind of photos with individual parents and their siblings. Everyone in families has gathered for big event, many times from far flung regions of country.
Their child's wedding may well be first time brothers and sisters have gotten together in years. It may be many years in future before they are ever together again. If opportunity to take these group photos is passed over because nobody thought much about importance of this fleeting opportunity, then those photos may end up never being captured. These photos often turn out to be most important and most appreciated of all photos I take regularily at wedding.
I'd be willing to bet that less than 10 percent of wedding photographers plying their trade today know to get these photos for you. You will have to specifically ask for them to be taken, or they just won't be done!
Other important people that most photographers will probably overlook photographing for you at wedding, unless you give them your written photo request list, are bride and/or groom's god parents, groups of bride and/or groom's co-workers, high school friends, youth camp friends, fellow fraternity and sorority members, fellow sports team members for high school or college.
The one thing no wedding photographer can do is look at a room full of total strangers and figure out how they interlock with each other just by looking! I gave up trying to do that after photographing my very first wedding 40 years ago! Now I send each bride an email before wedding requesting exactly this sort of information, so that I don't end up missing anyone of importance to bridal couple on their special day.
You will want to see to it that your wedding photographer is thoroughly armed with this often overlook information, so that they will get these photos for you. Remember, your wedding photographer can't read your mind when it comes to who among those present on your wedding are important to you and need to be photographed with you.